NINGBO, March 3 (Xinhua) -- China on Monday resumed the construction of its first undersea high-speed railway tunnel as workers restarted the offshore drilling session amid the battle against the coronavirus outbreak.

As part of the railway connecting Ningbo and the island city of Zhoushan in east China's Zhejiang Province, the underwater passage is designed to have a length of 16.2 km and a maximum depth of 78 meters.

To avoid risks of the outbreak, the Ningbo Maritime Safety Administration conducted an online technical evaluation on Feb. 25 to make preparation for the construction resumption.

"The resumption came much earlier than we had expected," said Shi Chao, manager of the drilling project, stressing that the online application for licenses and port entry and online recruitment had saved time and ensured steady construction progress.

The railway project will make Zhoushan accessible via trains and is expected to facilitate the integration of the Yangtze River Delta.

The length of China's railroad lines in service has exceeded 139,000 km, including 35,000 km of high-speed rail, ranking first in the world. Zhejiang is among the earliest provinces in the country to build high-speed rail.